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<b>db_env_set_func_file_map</b>
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<b><pre>
#include &lt;db.h&gt;
<p>
int
db_env_set_func_file_map(int (*func_file_map)(DB_ENV *dbenv, char *path, size_t len, int is_rdonly, void **addr),
    int (*func_file_unmap)(DB_ENV *dbenv, void *addr));
</pre></b>
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<b>Description: db_env_set_func_file_map</b>
<p>The Berkeley DB library optionally uses the ability to map a file into memory.</p>
<p>The db_env_set_func_file_map method configures all operations performed by a process and
all of its threads of control, not operations confined to a single
database environment.</p>
<p>Although the db_env_set_func_file_map method may be called at any time during the life of
the application, it should normally be called before making calls to the
<a href="../api_c/env_class.html">db_env_create</a> or <a href="../api_c/db_class.html">db_create</a> methods.</p>
<p>The db_env_set_func_file_map method
returns a non-zero error value on failure
and 0 on success.
</p>
<b>Parameters</b> <br>
 <b>func_file_map</b><ul compact><li>The <b>func_file_map</b> parameter is the function which maps a file
into memory.  The function takes 5 parameters:
<br>
<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul>
<b><b>path</b></b><ul compact><li>The <b>path</b> parameter is the name of file.  Repeated requests for
the mapping of the same name should return a reference to the same
memory.</ul>
<b><b>len</b></b><ul compact><li>The <b>len</b> parameter is the length, in bytes, of the file.</ul>
<b><b>is_rdonly</b></b><ul compact><li>The <b>is_rdonly</b> parameter will be non-zero if the mapped file is
read-only.</ul>
<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the memory location into which a pointer
to the mapped file is returned.</ul>
<br>
<p>The <b>func_file_map</b> function must return the value of <b>errno</b> on
failure and 0 on success.</p></ul>
 <b>func_file_unmap</b><ul compact><li>The <b>func_file_unmap</b> parameter is the function which unmaps a
file from memory.  The function takes 2 parameters:
<br>
<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul>
<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the value returned by the
<b>func_file_map</b> function when the file or region was mapped into
memory.</ul>
<br>
<p>The <b>func_file_unmap</b> function must return the value of <b>errno</b> on
failure and 0 on success.</p></ul>
<br>
<br><b>See Also</b>
<a href="../ref/program/runtime.html">Run-time configuration</a>
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